Radiant heating systems have become an increasingly popular way to heat homes, offices, and other buildings because they are more efficient than traditional heating systems.
A radiant heating system, such as the system 100 shown in FIG. 1, runs tubing 102 containing heated fluid 104, normally water, under each floor 106 of the building which is to be heated. The fluid is normally heated in a heater 108, containing a heating element 110 which is controlled electronically by a controller 112. The controller responds to an outdoor temperature sensor 125 placed on an outdoor wall to determine to what temperature the heater 108 should heat the system's water. Each room has a thermostat 114 located in it which causes a valve 115 to turn off the flow of heated water to tubing 102 under that room's floor if its temperature exceeds a temperature set on its thermostat. This could happen if something such as sunlight coming in windows, the use of a wood stove, or a crowd of people causes the room to be hotter than expected.
The tubing is commonly one half inch in diameter and is made of plastic. It is evenly spaced under the floor, as is indicated by the snaking of the tube 102 in FIG. 1 between the floor joists 124, so the floor is evenly heated. To further facilitate the even distribution of heat from the tubing, conductive heat shields 116, having parallel grooves for holding the tubing, are used. The tubing is placed in the grooves of the heat shield and the shields are nailed or stapled to the underside of the floor 106. These shields are normally made of a thin layer of conductive metal, such as sheets of aluminum approximately 0.012 to 0.022 thick. They help conduct heat away from the tubing and help evenly distribute it to the underside of the floor.
As a result of the even distribution of heat to the floor 106 there is little convection, so the heat rises up evenly from the floor, largely from conduction and radiation, as is indicated by the arrows 118 in FIG. 2. FIG. 2 shows the walls 120 and floor 106 of a room 122 in cross section. Below the floor 106 FIG. 2 shows the floor joists 124, the tubing 102, the heat shield 116, thermal insulation, such as fiberglass, 126, and the ceiling 128 of the room below.
FIG. 3 is a cross section of a room 122A similar to the room 122 shown in FIG. 2, except that room 122A has a more traditional wall mounted heater 130 through which a metal tube 132 carrying hot water runs. This more traditional heater does not conduct or radiate heat evenly throughout the room. Instead it relies on the convection currents 134 generated by the air it heats to distribute the heat is supplies to the room.
The radiant heating system shown in FIG. 2 has several advantages over the convection based heading system shown in FIG. 3. First, because the radiant heating system does not require convection to distribute its heat, it does not have to heat air to a temperature sufficiently high to cause efficient convection. As a result, radiant heating systems normally only have to heat their water to between ninety and one hundred and twenty degrees, whereas traditional convection based heating systems normally heat their water to about one hundred and eighty degrees. Operating with a lower water temperature is more efficient, because it causes less radiation from the portions of the system which are not delivering heat to places that are to be heated.
Radiant heating has another advantage in that the heat it generates is more even. Unlike convection based heating, which produces much hotter air near the heating element than far away from it, radiation based heating provides relatively even heat across the area of a room.
Because radiant heat greatly reduces the amount of convection, it greatly reduces the amount of heat that escapes up stair wells or that hovers near high ceilings. In fact, radiant heating systems can be designed so the heat they deliver is largely concentrated in the first six or seven feet above the floor. This enables a single floor to be heated without having heat escape to a different floor or to high ceilings.
FIG. 4 show an end view of a typical prior art heat shield 116A used with radiant heating systems under hardwood floors. It is formed of a thin sheet of aluminum containing two elongated grooves 136 into which the tubing 102 of the radiant heating system can be pushed, as is indicated by the arrows in that figure. Each groove have a generally circular shape, which is sized so that it will contact much of the surface of the tubing which is placed into it. The arc formed by the cross section of each groove is positioned so it will hold the tube against the bottom of the flooring against which the heat shield is placed.
Although prior art head shields, such as the shield 116A shown in FIG. 4 do a good job of conducting heat away from the tubing 102 and evenly distributing it to the underside of a wooden floor, it has the problem of being somewhat difficult to install, as will be explained with regard to FIGS. 5A-5F. These figures illustrate the steps normally used to install such a heat shield and its associated tubing. FIG. 5A shows a cross section of a portion of a wooden floor, with two floor joists 124, a first layer of wooden flooring 140, which is normally comprised of three quarter inch plywood. On top of it is placed a layer of hardwood flooring 142, which is usually approximately three quarters of an inch thick. The individual pieces of the hardwood flooring are held in place with nails 144, which are normally two inches long. These nails are normally driven into the sides of the pieces of hardwood so they will not show once the hardwood floor is complete. As a result, these nails normally stick out from the bottom of the first layer of flooring 140 by roughly three quarters of an inch.
Since these nails stick down through the bottom of the first layer of flooring by so much, the heat shield and its accompanying tubing can not be put in place before the hardwood floor is put down, or else the nails might puncture the tubing and ruin the thermal heating system. Instead the heat shield is not installed until the hardwood floor has been nailed down, as shown in FIG. 5A and then the portions of the nails 144 which stick down from the bottom of the first layer of flooring have been cut off, as shown in FIG. 5B. Once this has been done the heat shield and tubing can be installed. This is done by installing the tubing 102 between the joists 124 so that a long enough loop of it hangs down between the joists to fill the two grooves of the heat shield 116A, as is shown in FIG. 5C. Then the tubing is placed into the grooves of the heat shield, as is shown in FIG. 5D. Then the heat shield with the tubing contained in its grooves is nailed or stapled up to the underside of the first layer of flooring, as shown in FIG. 5E. Once this is done, thermal insulation 126 can be installed between the floor joists under the heat shield, and then a ceiling, such as the ceiling comprised a layer of plasterboard 146 covered with a skim coat of plaster 148, can be placed under the floor joists.
The prior art heat shield 116A and the method of installing it under hardwood floors has several disadvantages.
First, it requires the portions of the nails used to hold the hardwood flooring which stick down from the underside of the first layer of flooring to be clipped so the heat shield can be placed in contact with, or in close proximity to, the underside of that floor. Since it is usually difficult to clip all portions of the nails which stick down, this means the heat shield does not normally make as good a contact with the underside of the flooring as is desired.
Second, installing the tubing 102 in the grooves on the top side of the heat shield, as is shown in FIG. 5D, while the tubing is hanging down from holes in the joists and the heat shield is being held up in the air is less easy than could be desired.
Third, having to perform the plaster skim coating of ceiling below a floor after hardwood has been placed upon it has problems, since it is normally preferably to perform all major plastering in a construction project before hardwood floors are put down, because the spattering and moisture associated with plastering can be harmful to hardwood's finish.